As a processing apparatus for performing film forming processing on substrates, there is known, as shown in FIG. 1, a sputtering apparatus 100 equipped with: a transfer chamber T; a transfer robot 1 having two robot hands 12a, 12b which are housed in the transfer chamber T; and two load-lock chambers A, B and two film forming chambers C, D which serve as processing chambers, all being disposed in a manner to enclose the transfer chamber T.
In the above-mentioned sputtering apparatus 100, substrates which are handled by the unit of a lot (e.g., 25 substrates) and which are housed inside substrate containers 4 placed in position on a loading port 3, are alternately charged by a robot 30 into the load-lock chambers A, B, and the charged substrates are respectively transferred to the film forming chambers C, D by the transfer robot 1. Then, the same film forming processing is performed on the substrates in parallel with each other in the two film forming chambers C, D.
When the same processing is performed on the substrates in parallel with each other in the two film forming chambers C, D, in case, e.g., the time required for processing the substrates in the load-lock chambers A, B is longer than the time required for processing the substrates in the film forming chambers C, D, or in case the speed of the transfer robot 1 or of the robot 30 is so low as to cause a rate-determining step (bottleneck), and the like, the substrates cannot be discharged (also called “moved out”) right after the completion of the processing in each of the film forming chambers C, D. As a result, waiting time occurs. If this waiting time can be effectively shortened, a further improvement in the throughput can be attained.
By the way, it is known that the sputtering apparatus 100 is applied to the forming of a titanium nitride (TiN) film, e.g., by reactive sputtering (see, e.g., patent document 1). When film forming is made of titanium nitride, there is a problem in that, with an increase in the number of substrates that have been processed, the number of particles to be accumulated on the surface of the substrate, during film forming, will increase. As a solution, when the number of substrates that have been processed in the processing chambers has reached a predetermined number (that may be set arbitrarily), Ti target is shielded by a shutter which prevents the sputtered particles of the target from getting scattered, thereby performing a dummy sputtering processing (so-called recovery processing). This kind of dummy sputtering processing is performed, e.g., each time the processing by the unit of a lot is finished. In other words, when 25 substrates are supposed to make one lot, when the number of the substrates processed in any one of the film forming chambers has reached a predetermined number (12 substrates), the dummy sputtering processing is started in said one of the film forming chambers. When the number of the substrates processed in the other of the film forming chambers has reached a predetermined number (13 substrates), the dummy sputtering processing is started in said the other of the film forming chambers. At this time, if the time required for dummy sputtering processing is longer than the time required for processing of substrates in the film forming chambers, the dummy sputtering processing will be performed in the two film forming chambers in a manner overlapped with each other. In such a case, it will be similar to the case in which the processing for a predetermined period of time is interposed in both the film forming chambers between the two lots. Therefore, this solution does not contribute to the shortening of the waiting time.